Comics readers were understandably a little confused when we all saw that Chiwetel Ejiofor’s character Baron Mordo was in Doctor Strange, but in a considerably different way than everyone expected. If you know Doctor Strange, you know that Baron Mordo is actually his archnemesis: the two met while both under the tutelage of the Ancient One, and Mordo is eventually cast out after Strange foils his attempt to kill their teacher. Mordo becomes a magician gifted in the black arts, and antagonizes Strange at every turn.

It was a difficult character, [a] very difficult character to adapt because of the very basic archness that he plays all the way through there.

He explained that he wanted to give Mordo a kind of origin story alongside Strange. At his first appearance in the comics, Mordo is just said to be Strange’s arch-nemesis, with no reason why.

I felt that we had to start by establishing who he was before he got into that arch villainy in the comics. That’s a lot of what we're doing in this movie.

We’re sort of building a foundational understanding of who he was before the guy that you met in that comic, so that that turn isn’t an arch turn.

So we’ll definitely see Mordo in full villain mode at some point. The MCU usually gives its villains plenty of backstory so that the audience knows at least where they’re coming from when they eventually turn against the hero. Loki became a fan favorite after Thor and The Avengers simply because he was given just as rich a characterization as the God of Thunder, so we can expect Doctor Strange to treat Baron Mordo with the same amount of nuance.

This probably means Mordo will be back sometime later, whether its for a Doctor Strange sequel or even earlier. Who knows, maybe he’ll team up with Thanos for Infinity War, and then the Avengers will really be in some trouble.